1. Field of the Invention
The present invention relates to an object detecting device for detecting an object in a targeted area based on a state of reflected light when light is projected onto the targeted area, and an information acquiring device incorporated with the object detecting device.
2. Disclosure of Related Art
Conventionally, there has been developed an object detecting device using light in various fields. For instance, in a laser radar system to be loaded in a vehicle, laser light is projected in the forward direction of the vehicle to determine whether an object exists in the forward direction of the vehicle based on presence or absence of reflected light at the light projection. Further, a distance to the object is detected, based on a timing at which laser light is projected and a timing at which reflected light is received. In addition to the above, an object detecting device using infrared light is loaded in an arcade game machine, a security system, or a like device to detect presence or absence of e.g. a person or a gesture thereof.
In such an object detecting device, light in a predetermined wavelength region is projected from a laser light source or a Light Emitting Diode (LED) to a targeted area. In this case, precision of object detection is enhanced by disposing a filter for guiding only light in the predetermined wavelength region to a light receiving element such as a Position Sensitive Detector (PSD) or a CMOS image sensor.
In particular, in the case where the object detecting device is used outdoors, detection precision may be degraded due to sunlight. FIG. 17 is a diagram showing a frequency spectrum of sunlight. About 40% of sunlight on the ground lies in a infrared wavelength region. Therefore, it is required to properly block the sunlight, in the case where infrared light is used for object detection.
In the above case, for instance, a laser light source for emitting light in a narrow wavelength region may be used as a light source, and a narrow wavelength filter having the wavelength region of the laser light source as a transmission region may be used. Even with use of the above members, since the emission wavelength region has a tolerance in each laser light source, it is not impossible to completely coincide the transmission region of the filter with the transmission region of the laser light source. Further, since the emission wavelength region of laser light changes as the temperature of a light emitting portion changes, mismatching may occur between the emission wavelength region of laser light and the transmission region of the filter depending on a use condition.